Determination of Total Nitrogen in Natural Waters

Abstract

AbstractA simple, precise, and rapid method for estimating total N (to include nitrate and nitrite) in natural water is given. The proposed method involves evaporation of the water sample, pretreatment of the evaporated sample with reduced iron and H2SO4 to reduce nitrate to ammonium, and subsequent Kjeldahl digestion of the sample to recover organic N. Evaporation, pretreatment, and digestion of samples are accomplished in Folin‐Wu nonprotein tubes. Ammonium in the digest is estimated by steam distillation and subsequent titration. Evaluation of the proposed method revealed that the recovery of nitrate N and organic N in samples was affected by the amount of reduced iron added (200 mg was satisfactory), by the brand of reduced iron used (several preparations were satisfactory), and by gently boiling the sample with reduced iron and H2SO4 prior to digestion. The proposed method was effective in recovering nitrate N and organic N from water solution over a wide range in concentration and the method was successful in recovering nitrate N and organic N added to filtered and unfiltered river and pond water samples. The precision of the proposed method was satisfactory for total N analysis of water samples, and the method appears adequate for estimation of total N in most water and waste water samples.